detect 110v ac circut

Discussion in 'The Projects Forum' started by godfather55v, Jul 26, 2016.

  1. godfather55v

    Thread Starter New Member

    Jul 26, 2016
    1
    0
    I have a 110v AC circuit i want to detect when it is on or off w/ a raspberry pi gpio pins.
     
  2. #12

    Expert

    Nov 30, 2010
    16,298
    6,810
    A diode into 2 resistors to reduce the voltage from 170 V peak to whatever the range of your chip. 3.3v? 5v?
    then a capacitor to hold the peak value for most of a second. The measured voltage will bleed off through the resistors when the input stops.

    There is another method with an opto-isolator if that is necessary.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,654
    632
    Or simply, connect a 110 V lamp to the 110V and watch it with a light detector shield.
     
  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,540
    1,251
    Or plug in a $2 USB wall wart and use the 5 V output as a logic signal. Put a 47 ohm 2 W resistor across the output to shorten the detection time.

    Don't the house rules mandate a galvanic isolation method?

    ak
     
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